Put certificates for your domains here, one directory per domain and
certificate pair:

- mx.example.com/
  - fullchain.pem  Certificate (full chain).
  - privkey.pem    Private key.

Note the directory structure matches certbot's structure, so if you use it you
can just create symlinks to /etc/letsencrypt/live/<domain>.

Note also that the certificates and private keys must be readable by the
chasquid user.
